From: Judy Seigel (jseigel@panix.com)
Date: 09/09/02-11:33:04 PM Z
On Mon, 9 Sep 2002, Christina Z. Anderson wrote:
> ....That Sudre uses a formula more akin to bleach etch and NOT a
> true mordanting formula is the case.
> The differences between the two are that mordancage (actually really
> bleach etch or gelatin relief) is a reverse relief process; dye mordanting
> has no relief whatsoever. The gelatin surface remains level. Mordancage
> uses hydrogen peroxide as the catalyst to dissolve the gelatin. Dye
> mordanting just changes the gelatin in the print to one that accepts basic
> dyes in direct proportion to the darks, usually with thiocyanate combined
> with copper. The formulae seem similar except for the lack of hydrogen
> peroxide in dye mordanting.
In the literature I found, the etch technique is called both Mordancage
and etch bleach, probably by period... I think it's also called Mariage
(for M. Mariage, or Marriage), or that's what Pierre Cordier called it.
The dye process seems quite different (to me anyway), but I note in
passing that some of those dye mordanting bleaches were/are excellent for
regular bleach & redevelop toning, often making distinct color variants.
> Still, bleach etch does not necessarily result in a negative gelatin
> relief. It can run the gamut from a negative to part negative and positive,
> because the highlights in a print do not dissolve, and when redeveloped,
> remain positive.
True, the highlights don't dissolve with the peroxide (only developed--
metallic -- silver is destroyed). But if you re-expose the print to light
at this point, which you do in the process I did, the highlights develop
up black. Or maybe not fully black, since the handling lowers D-max, but
not really positive any more. Is there some way of keeping them white?
> Nate Apkon is currently testing out dye mordanting, and it will be
> interesting if this process still has visual interest to us today. I know
> mordancage does for me.
> Chris
The dye method, which seems relatively clunky & uncertain, probably filled
a need/desire for color that's more readily filled by other methods today.
Or maybe not... Will we get a news flash?
J.
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